The continuing expansion and world-wide growth of technically sophisticated industries such as those concerned with computers and computer based products including telecommunications equipment have led to concomitant expansion and growth in support industries, particularly those concerned with power supplies. Larger, sophisticated computer installations have been seen to require assured high quality input power supplies not generally available directly from the line outputs of utilities. Accordingly, a wide range of somewhat elaborate power improvement approaches are employed by industry.
Early efforts to overcome the aberrations of line power supplies have evolved a variety of power conditioning devices, for example, uninterruptible power supplies (UPS) using a battery charger, batteries, an inverter, and static switch arrangement which may be installed to evoke waveform re-creation. Further, motor generators have been provided to achieve power assurance. In some approaches, systems have been provided which modify, but do not recreate waveforms, for example, such as voltage regulators or spike suppressors. The latter systems basically are ineffective in the treatment of a variety of adverse conditions which may be encountered. Over the recent past, a polyphase ferroresonant voltage stabilizer or synthesizer has been successfully employed in the marketplace. In their elementary form, such synthesizers comprise a regulator which is fashioned as a non-linear saturable transformer arrangement in parallel with a capacitor assembly which is supplied from the line source through an input inductor. The saturable transformer components and capacitors form a ferroresonant circuit wherein the reactive components operate beyond the knee of a conventional magnetization curve. Such device, for example, are described in U.S. Pat. Nos. 4,305,033 and 4,544,877 by Jeffrey M. Powell.
More recently, utility interactive systems have been proposed which function to independently generate a sinewave output and which are connected to a utility through some form of inductor. Employing batteries as an independent source, these devices operate with four quadrant inverters and the like in conjunction with a battery second source to skew the phase relationship of the inverter function with the utility line input to develop a selective reactive power flow. These utility interactive systems exhibit excellent power factor characteristics and impose very low distortion on the utility with which they interact.
As the capability and capacities of the conveniently priced and sized personal computers and word processing systems have improved, their utility has expanded to an extensive diversity of applications. Correspondingly, these devices and their applications have become more and more critical to the operations of industry. Thus, business and industry have sought a highly reliable utility power line input treatment technique which is available at a price commensurate with the personal computer and the word processor and which exhibits performance characteristics of high reliability and efficient operation. To complement the relatively small size of these personal computers, such power treatment devices must be fabricable in compact size and convenient in shape. Further, the devices should incorporate a UPS feature providing for self-contained battery operation in the event of line power failure. While this uninterruptible power feature is needed, its performance duration may be limited concomitantly with those power outage problems typically encountered by the personal computer or word processor user.